U.S. patent number 6,673,302 [Application Number 09/768,490] was granted by the patent office on 2004-01-06 for wet processing method for catheter balloons.
This patent grant is currently assigned to SciMed Life Systems, Inc.. Invention is credited to Mona Dahdah, Ron Drake, Daniel Horn, Lixiao Wang.
United States Patent |
6,673,302 |
Wang , et al. |
January 6, 2004 |
Wet processing method for catheter balloons
Abstract
A process for blowing a balloon from a tubular parison of a
thermoplastic polymer material by radially expanding the parison at
an elevated temperature and pressure, the process characterized in
that: a) the polymer material includes a "H-bonding" polymer which
undergoes interchain hydrogen bonding between at least some
segments thereof; b) the parison is conditioned in a high moisture
environment prior to blowing, and c) the balloon is blown after
moisture conditioning of the parison and without an intervening
drying thereof. H-bonding polymers may be polyamides, polyurethanes
or block copolymers containing a polyamide or polyurethane block.
The process reduces occurrence of fish eye defects in the formed
balloons.
Inventors: |
Wang; Lixiao (Long Lake,
MN), Dahdah; Mona (West St. Paul, MN), Drake; Ron
(St. Louis Park, MN), Horn; Daniel (Shoreview, MN) |
Assignee: |
SciMed Life Systems, Inc.
(Maple Grove, MN)
|
Family
ID: |
25082645 |
Appl.
No.: |
09/768,490 |
Filed: |
January 24, 2001 |
Current U.S.
Class: |
264/523;
264/211.12; 264/527; 264/532 |
Current CPC
Class: |
A61M
25/1029 (20130101); B29B 13/023 (20130101); B29C
49/0005 (20130101); B29C 35/049 (20130101); B29K
2075/00 (20130101); B29K 2077/00 (20130101); B29L
2031/7542 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); B29B 13/02 (20060101); B29B
13/00 (20060101); B29C 49/00 (20060101); B29C
35/04 (20060101); B29C 049/04 (); B29C 049/08 ();
B29C 049/18 () |
Field of
Search: |
;264/523,530,209.1,516,527,532,211.12,178R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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274 411 |
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Jan 1988 |
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EP |
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0 420 488 |
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Apr 1991 |
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EP |
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0 485 903 |
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May 1992 |
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EP |
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0 513 459 |
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Nov 1992 |
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EP |
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0 540 858 |
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May 1993 |
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EP |
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0592885 |
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Sep 1993 |
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EP |
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0 566 755 |
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Oct 1993 |
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EP |
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2 651 681 |
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Mar 1991 |
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FR |
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84/01513 |
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Apr 1984 |
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WO |
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92/08512 |
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May 1992 |
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WO |
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92/19316 |
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Nov 1992 |
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WO |
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95/23619 |
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Sep 1995 |
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WO |
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96/04951 |
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Feb 1996 |
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WO |
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97/326247 |
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Mar 1996 |
|
WO |
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96/12516 |
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May 1996 |
|
WO |
|
Other References
Flesher, "Polyether block amide, high-performance TPE," Modern
Plastics, Sep. 1987 pp. 100, 105, 110. .
Koch, "PEBAX (Polyether Block Amide)", Advances in Polymer
Technology, vol. 2, No. 3 1982 pp. 160-162. .
De, et al. eds. Thermoplastic Elastomer from Rubber-Plastic Bends,
Chapter1, Ellis Horwoal, New York pp. 13-27. .
Gorski, The Nomenclature of Thermoplastic Elastomers, Kunstoffe
German Plastics, 83 (1993) No. 3, pp. 29-30. .
Hofmann, Thermoplastic Elastomers, Kunstoffe German Plastics, 80
(1990) No. 10, pp. 88-90. .
Atochem, "Pebax .RTM. Resins 33 Series Property Comparison"
undated, (1 pg manufacturers technical information sheet received
Sep. 29, 1994. .
Atochem, undatd and untitled brochure for Pebex .RTM. resins, pp.
2-5. Not available. .
Bhowmick, et al. eds., Handbook of Elastomers, Chapters 10 and 12,
Marcel Dekker Inc., pp. 341-373 and 411-442. .
Walker, et al. eds. Handbook of Thermoplastic Elastomers, Chapter
8, Van Nostrand Reinhold Co., NY pp. 258-281. .
U.S. application Ser. No. 09/672330, Nao Pao Lee et al., filed Sep.
2000..
|
Primary Examiner: Colaianni; Michael
Assistant Examiner: Fontaine; Monica A
Attorney, Agent or Firm: Vidas, Arrett & Steinkraus
PA
Claims
What is claimed is:
1. A process for blowing a balloon from a tubule parison of a
thermoplastic polymer material by radially expanding the parison at
an elevated temperature and pressure, the process characterized in
that: a) the polymer material comprises a H-bonding polymer, the
H-bonding polymer being a polymer which undergoes interchain
hydrogen bonding between at least some segments thereof; b) the
prison is conditioned in a high moisture environment prior to
blowing, wherein the high moisture environment is a high humidity
atmosphere of at least 80% relative humidity at ambient
temperature, and c) the balloon is blown after moisture
conditioning of the parison and without an intervening drying
thereof.
2. A process as in claim 1 wherein the balloon so formed is
subsequently equilibrated at ambient relative humidity.
3. A process as in claim 1 wherein the high humidity atmosphere is
at least 85% relative humidity at ambient temperature.
4. A process as in claim 3 wherein the high humidity atmosphere is
at least 90% relative humidity at ambient temperature.
5. A process as in claim 1 wherein said H-bonding polymer is a
polymer having N-H groups along at least a portion of the length of
the polymer chain or on groups pendant thereto.
6. A process as in claim 1 wherein said H-bonding polymer is
selected from the group consisting of polyamides, polyurethanes,
and block copolymers containing polyamide or polyurethane
segments.
7. A process as in claim 6 wherein said H-bonding polymer is a
polyamide.
8. A process as in claim 7 wherein said polyamide is selected from
the group consisting of nylon 6, nylon 6/6, nylon 6/10, nylon 6/12,
nylon 9, nylon 11, nylon 12, polyamides prepared bypolycondensing
xylylenediamine with an aliphatic dicarboxylic acid, and polyamides
prepared by polycondensing isophthalic acid and an aliphatic
diamine.
9. A process as in claim 6 wherein said H-bonding polymer is a
polyurethane.
10. A process as in claim 6 wherein said H-bonding polymer is a
block copolymer containing polyamide or polyurethane segments.
11. A process as in claim 10 the block copolymer is a
polyamide-polyether-polyester.
12. A process as in claim 1 wherein the thermoplastic polymer
material is a polymer blend comprising at least one said H-bonding
polymer.
13. A process as in claim 1 wherein the parison is a multi-layer
laminate at least one layer of which is composed of said H-bonding
polymer.
14. A process as in claim 1 wherein the parison is conditioned for
a time in excess of one hour which is sufficient to produce a
moisture content growth rate which is 10% or less of the moisture
content growth rate growth rate in the first hour of
conditioning.
15. A process in claim 14 wherein said conditioning time is
sufficient to produce a moisture content growth rate which is 5% or
less of the moisture content growth rate growth rate in the first
hour of conditioning.
16. A process as in claim 15 wherein the conditioning time is
sufficient to produce a substantially equilibrated moisture
content.
17. A process as in claim 1 wherein the parison is conditioned in
said high moisture environment by soaking in liquid water.
Description
Balloons are widely used on medical devices, such as catheters,
employed in various medical treatments. Examples of such treatments
include repair of the vascular system, e.g. angioplasty, stent
placement, and the like and in treatment and repair of disorders of
the gastrointestinal, bronchial or esophageal tracts. Such balloons
may be made of a wide variety of materials. With some of these
materials, namely polyamides ("nylons"), polyurethanes and block
copolymers comprising polyamide or polyurethane segments, hydrogen
bonding between chains of the molecule plays a significant role in
the strength profile of the formed balloon.
U.S. Pat. No. 4,906,244 issued in March 1990 to Pinchuk et al
describes balloons of certain aliphatic polyamides and states that
"nylon materials have been observed to exhibit desirable stability
during processing to the extent that they do not absorb excessive
moisture from the environment if the parison is allowed to stand
uncovered for reasonable time periods."
U.S. Pat. No. 5,328,468 describes medical device balloons made of
an aromatic polyamide.
U.S. Pat. No. 5,556,383 describes medical device balloons made of a
block copolymer comprising polyamide segments.
EP 0592885 describes medical device balloons made of a
thermoplastic polyurethane.
U.S. Pat. No. 5,714,110 describes an improved method of preparing
an oriented balloon of thermoplastic material comprising extruding
a hollow tube of the thermoplastic material and subsequently
expanding the tube by subjecting the tubing, while in a mold, to an
elevated temperature and an increased interior pressure to produce
an oriented balloon, the invention being characterized in that the
tube is subjected to a drying step, prior to the expanding step,
thereby increasing the strength of the balloon relative to a
reference balloon prepared in the same manner, except for said
drying step.
Hence until now it has been considered that the moisture content of
a parison of thermoplastic polymer material used to form a medical
balloon was not a particular concern, or that if it was a concern,
the parison should be dried before blowing the parison into a
balloon.
In forming balloons by radial expansion of a tubular parison it is
often necessary to use a very high blowing pressure to initiate
radial expansion at conventional blowing temperatures of about
90.degree. C. to about 110.degree. C. Once initiated, however, the
high pressure causes very rapid growth as the polymer material gets
increasingly thinner, until the expanding polymer material reaches
the mold wall. This rapid growth has been associated with a number
of common defect problems, such as balloons displaying "fish eye"
defects.
In copending U.S. application Ser. No. 09/672,330, filed Sep. 28,
2000, it is taught that a slower balloon growth rate can reduce
fish eye defects, but the technique of obtaining a lowered growth
rate in that application requires modification of parison
configurations.
SUMMARY OF THE INVENTION
It has now surprisingly been discovered that significant benefits
can be obtained in forming a balloon from a parison of a
thermoplastic polymer which undergoes substantial intermolecular
hydrogen bonding, when the parison is conditioned in a high
humidity environment prior to blowing the balloon. Accordingly the
invention in one aspect is a process for blowing a balloon from a
tubular parison of a thermoplastic polymer by radially expanding
the parison at an elevated temperature and pressure, the process
characterized in that: a) the polymer is one which undergoes
hydrogen bonding between at least some segments thereof ("a
H-bonding polymer"); b) the parison is conditioned in a high
moisture environment prior to blowing, and c) the balloon is blown
after moisture conditioning of the parison and without an
intervening drying thereof.
Moisture conditioning is continued for a time sufficient to obtain
a stable reproducible high moisture content, suitably about 8 hrs
or more in an environment of at least 80% RH.
Further aspects of the invention will become apparent from the
detailed description which follows.
DESCRIPTION OF THE FIGURES
FIG. 1 is a fragmentary side view of a medical catheter having
mounted thereon a balloon produced in accordance with the
invention.
FIG. 2 is a fragmentary side view of an extruded tubular parison
suitable for use in preparing a balloon in accordance with the
invention.
FIG. 3 is a schematic side view of a portion of a balloon produced
in accordance with a prior art procedure and displaying a
"fish-eye" defect.
FIG. 4 is a graphical presentation of moisture uptake in parisons
of Pebax.RTM. 7233 resin under conditions as specified below.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1 there is shown therein a medical device
catheter 8 having mounted thereon a balloon 10, suitable for
mounting on a catheter. Balloon 10 comprises oppositely disposed
waist portions 11, 12, cone portions 13, 14, and body portion 15.
Balloon 10 is made from polymer material.
The polymers employed in the inventive process which have hydrogen
bonding sites, particularly N--H groups along the length of the
polymer chain or on groups pendant thereto. Polyamides,
polyurethanes, and block copolymers containing polyamide or
polyurethane segments are preferred examples of such polymers.
Thermoformable graft or comb copolymers comprising polyurethane
and/or polyamide segments may also be used.
Polyamides may be aliphatic or aromatic. Examples of aliphatic
polyamides include nylon 6, nylon 6/6, nylon 6/10, nylon 6/12,
nylon 9, nylon 11 and nylon 12, Examples of aromatic polyamides
include polyamides prepared by polycondensing xylylenediamine with
an aliphatic dicarboxylic acid such as adipic acid, and polyamides
prepared by polycondensing isophthalic acid and an aliphatic
diamine such as hexamethylenediamine. Nylon MXD6 and nylon 6I,
manufactured by Mitsubishi Gas Chemical Company, Inc., are specific
such polymers.
Polyurethanes may be any thermoplastic polyurethanes suitable for
use in forming balloons including polyurethanes derived from
polyester polyols or polyether polyols or mixtures thereof and
aromatic or aliphatic polyisocyanates. Such polyurethanes may be
elastomeric or engineering polymers. Specific examples of
polyurethanes include Tecothane.RTM. aromatic
polyurethane-polyether polymers, and polyurethane-polyethers and
polyurethane-polyesters sold under the Pellethane.RTM. trademark by
Dow, for instance and Pellethane.RTM. 2102, 2103, 2202, 2353, 2354,
2355 and 2363. Bionate.RTM. polycarbonate-urethane polymers from
Polymer Technology Group, Inc., for instance Bionate.RTM.80A may
also be used. Engineering polyurethanes may also be used, for
instance Isoplast.RTM. polyurethanes, such as Isoplast.RTM. 301,
sold by Dow and Tecoplast TP-470 Series resins sold by Thermedics,
Inc.
Block copolymers include segmented polyamide-polyether-polyesters
sold under the Pebax.RTM. trademark, in particular Pebax 6333,
Pebax 7033 and Pebax 7233, and aliphatic polyurethane-polyether
block copolymers, sold by Thermedics, Inc., under the Tecoflex.RTM.
mark, for instance Tecoflex.RTM. 80A. Some of the polyurethanes
listed in the previous paragraph may be block copolymers.
Polymer blends may also be used in some cases, typically comprising
at least one member of the blend being a polymer from the group
described above. Preferably, such a blend would be a compatible
mixture of a thermoplastic elastomer resin and a thermoplastic
engineering resin.
The balloon wall may be from a single layer of the polymer material
which engages in interchain hydrogen bonding, or such polymer may
be one layer of a laminate balloon composed of two or more layers
of thermoplastic polymer.
For polymer materials which engage in interchain hydrogen bonding,
the presence of moisture has been considered to weaken such
interchain bonding, in some cases lowering tensile strength up to
as much as 45%. This is generally undesirable in the final balloon.
However, such tensile strength weakening facilitates processing,
resulting in a substantial reduction in processing defects such as
"fish eye" defects (also referred to as "football" defects.
Furthermore, excess moisture can be removed from the formed balloon
after blowing, typically by equilibrating at ambient moisture, to
yield a balloon which has comparable burst strength to balloons
prepared without the parison moisture treatment step of the
invention. Typically the drying equilibration can be much more
rapid than moisture equilibration of the parison because the much
thinner balloon wall rapidly loses excess moisture in a drier
atmosphere.
Catheter balloons, such as depicted in FIG. 1, may be formed from
tubular extrusions of the polymer material. Tubular extrusions may
be prepared according to conventional procedures and segmented to
form tubular parisons from which the medical device balloons will
be formed. An extrusion of this type is depicted as 20 in FIG.
2.
The parisons may be formed of a single layer of polymer material or
of multiple layers of the same or different polymers. Multilayer
parisons may be formed by coextrusion or by other techniques known
in the art.
For medical catheter balloons suited for dilatation or stent
placement applications with nominal diameters of about 1.5-24 mm,
extruded wall thicknesses (single wall basis) in the range of
0.003-0.036 inch (0.076-0.91 mm) and outer diameters in the range
of 0.015-0.236 inch (0.38-6 mm) will typically be suitable.
After extrusion the parison is radially expanded into a medical
catheter balloon.
In accordance with the present invention, after extrusion and
before radial expansion the parison is conditioned in a moist
environment, suitably a moist atmosphere. As used herein a moist
atmosphere is considered to be at least 80% RH, ambient temp
(18-23.degree. C.), preferably at least 85% and more preferably at
least 90% RH at ambient temp. If desired a higher temperature may
be used with at least a corresponding mass quantity of moisture.
Conditioning time is an amount sufficient to provide a stable
reproducible high moisture content in the polymer. This will
generally be for a time in excess of 1 hr which is sufficient to
provide a moisture uptake rate in the parisons which is 10% or
less, preferably 5% or less of the moisture content growth rate in
the first hour of conditioning. Typical conditioning times will be
from about 8 to about 48 hours. Preferably the time is sufficient
to achieve substantial equilibration. Typically conditioning for a
period of 24 hours or less at ambient temperature will be
sufficient to achieve a state of substantial equilibration.
As an alternative to a moist atmosphere, the moist environment
conditioning may be accomplished by soaking the parison in liquid
water for a time sufficient to provide a stable reproducible
moisture content in the polymer. Depending on the particular,
liquid water soaking may require more or less time than moist
atmosphere conditioning.
Accelerated conditioning at elevated temperature and/or pressure
may be effective in some cases to shorten the conditioning
time.
The moisture conditioning may be done on the parison as extruded,
or on the parison after modification by performance of any desired
intermediate stretching, ID expansion and/or cone/waist reduction
steps, as known in the art. Alternatively, some or all of such
intermediate stretching, ID expansion and/or cone/waist reduction
steps may be performed after conditioning, promptly before
blowing.
The moist parison is then blown into a balloon without drying the
parison or allowing it to equilibrate at ambient RH. Any
conventional blowing technique may be employed. Free blowing may be
used, but typically parison will be expanded in a mold. Radial
expansion is performed at a temperature above Tg but below melting
temperature. For most suitable balloon materials the radial
expansion will typically be in the range of about 85-140.degree.
C., although in some cases temperatures as high as about
200.degree. C. may be feasible. For medical catheter balloons
internal pressure of about 100 (689 kPa) to about 500 psi (3447
kPa) will generally be used to blow the balloon.
If desired, a heat setting step can be run at a temperature higher
than the blow temperature (typically 5.degree.-25.degree. C.
higher) but at a pressure lower than the blowing pressure
(typically 20 psi (138 kPa) to about 100 psi (689 kPa). Heat
setting can reduce balloon compliance and can increase the burst
pressure of the balloon. Heat setting procedures which may be
adapted for use in the inventive process are described in EP 274
411 A2 (C. R. Bard) and EP 592 885 A2 (C. R. Bard), both of which
are incorporated herein by reference.
If it is desired to increase compliance or to provide a stepped
compliance profile, the blown balloon, or a portion thereof may be
shrunk by heating to a temperature somewhat below the blowing
temperature (suitably to about 70.degree. C.-80.degree. C.) while
pressurizing to at about 30 psi (207 kPa) to about 100 psi (689
kPa). Shrinking procedures which may be adapted for use in the
inventive process are described in U.S. Pat. No. 5,348,538 (L.
Wang, et al) and in WO 97/32624, both of which are incorporated
herein by reference.
After the balloon has been blown and removed from the mold, excess
moisture introduced by the parison moisture conditioning step of
the invention can be easily removed, suitably by equilibration at
ambient RH for a storage time of at least 8 hours, preferably one
day or more.
The final product is a balloon as in FIG. 1.
As noted the process of the invention provides a lower level of
defects commonly encountered in molded balloons. A lower material
tensile strength is believed to produce a decrease in the strain
rate sensitivity of an expanding parison. This in turn allows for a
more uniform distribution of polymer material and produces a lower
defect rate. In particular the number and size of "fish eye" or
"football" defects is reduced. Balloon 33 in FIG. 3 includes a pair
of fish eye defects 36 on the body portion thereof. Fish eye
defects are believed to be due to regions in which polymer is
relatively more gelled than the adjacent polymer material, or to
the presence of localized microcontamination causing the defect
region to be stressed more. The gelled or microcontaminated
material, being less mobile, is not evenly redistributed if the
balloon expansion occurs too quickly. With a reduced balloon growth
rate the gelled material has time to redistribute itself more
uniformly in the polymer mass.
Because the inventive process reduces the occurrence of such
defects, a batch of about 50 or more, and preferably about 100 or
more, sequentially produced balloons from a single production run
is improved, relatively to a corresponding sequence of balloons
produced without the moisture conditioning step. As such a
sequential batch represents a distinctive and non-obvious
manufacture, even though the individual non-defective members
thereof may not be otherwise readily distinguishable.
Depending on the material and blowing techniques used yields of
balloons free of fish-eye defects may be improved by 5-50% or more
as a result of the use of a high moisture equilibrated parison in
accordance with the invention.
In one experimental study, with controlled variations of 14 process
variations using Pebax 7233 parisons, conditioning at approximately
90% RH, ambient temp, on average produced parison moisture contents
in the range of 14,000-20,000 ppm, as determined by Karl Fisher
titration. Ambient moisture content of the Pebax 7233 resin, per
manufacturer's data, was approximately 7000 ppm. Yields of fish
eye-free balloons made from parisons equilibrated at 90% RH before
blowing were on average 10.3% higher than yields obtained from
parisons stored at ambient RH of approximately 50%.
Referring to FIG. 4, there is shown a graph of Karl Fisher moisture
titration data for a group of parisons stored at 72.degree. F.
(22.degree. C.) at 92% RH, ambient pressure, for up to 24 hrs (1440
min). The moisture content initially increases rapidly from an
initial content of about 7000 ppm to a content of 9900 ppm after 62
min, corresponding to an initial uptake in the first hour slightly
in excess of 2800 ppm. The uptake rate continuously decreases,
however, such that by 8 hours the growth rate in ppm/hr is less
than 10% of the initial rate and the moisture content can be
considered to be acceptably conditioned. By 24 hours the moisture
content of about 16200 appears to be near an asymptotic limit
indicating that the moisture content is substantially
equilibrated.
Although the invention has been described especially in connection
with polyamides and polyurethane, it will be recognized that other
polymers which undergo interchain hydrogen bonding between at least
some segments thereof may also be employed in the invention. For
instance, polymers which form interchain links between H-donating
groups such as --OH, --NH, and --SH groups on one molecule and
receptor atoms on another molecule. Receptor atoms may be for
instance oxygen atoms of carboxyl, ether, or hydroxyl groups,
nitrogen atoms of an amine, amide, carbamate, cyano, isocyano, or
other N-containing group, or fluoro atoms.
While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
The above examples and disclosure are intended to be illustrative
and not exhaustive. These examples and description will suggest
many variations and alternatives to one of ordinary skill in this
art. All these alternatives and variations are intended to be
included within the scope of the claims, where the term
"comprising" means "including, but not limited to". Those familiar
with the art may recognize other equivalents to the specific
embodiments described herein which equivalents are also intended to
be encompassed by the claims. Further, the particular features
presented in the dependent claims can be combined with each other
in other manners within the scope of the invention such that the
invention should be recognized as also specifically directed to
other embodiments having any other possible combination of the
features of the dependent claims. For instance, for purposes of
claim publication, any dependent claim which follows should be
taken as alternatively written in a multiple dependent form from
all prior claims which possess all antecedents referenced in such
dependent claim if such multiple dependent format is an accepted
format within the jurisdiction (e.g. each claim depending directly
from claim 1 should be alternatively taken as depending from all
previous claims). In jurisdictions where multiple dependent claim
formats are restricted, the following dependent claims should each
be also taken as alternatively written in each singly dependent
claim format which creates a dependency from a prior
antecedent-possessing claim other than the specific claim listed in
such dependent claim below.
The entire contents of all documents and copending applications
mentioned anywhere in the present application are incorporated
herein by reference.
* * * * *